Scientists have created the ultimate GM crop: contraceptive corn. Waiving fields of maize may one day save the world from overpopulation.

The pregnancy prevention plants are the handiwork of the San Diego biotechnology company Epicyte, where researchers have discovered a rare class of human antibodies that attack sperm.

By isolating the genes that regulate the manufacture of these antibodies, and by putting them in corn plants, the company has created tiny horticultural factories that make contraceptives.

'We have a hothouse filled with corn plants that make anti-sperm antibodies,' said Epicyte president Mitch Hein.

'We have also created corn plants that make antibodies against the herpes virus, so we should be able to make a plant-based jelly that not only prevents pregnancy but also blocks the spread of sexual disease.'

Contraceptive corn is based on research on the rare condition, immune infertility, in which a woman makes antibodies that attack sperm.

'Essentially, the antibodies are attracted to surface receptors on the sperm,' said Hein. 'They latch on and make each sperm so heavy it cannot move forward. It just shakes about as if it was doing the lambada.'

Normally, biologists use bacteria to grow human proteins. However, Epicyte decided to use corn because plants have cellular structures that are much more like those of humans, making them easier to manipulate.

The company, which says it will not grow the maize near other crops, says it plans to launch clinical trials of the corn in a few months.